The Membrane Potential Flashcards
Know what a dendrite, axon, axon hillock, soma, and synaptic cleft are.
Do it.
What is a coulomb a measure of?
Electrical charge (charge transported by 1 Amp for 1 sec)
Coulombs of a proton?
1x10(-19) C
What is Avagadro’s #?
Molecules in a substance
6.022 x 10(23)
What is Faraday’s Constant?
Charge on a mole of any monovalent ion
Coulombs X Avagadro
What is voltage a measure of?
Potential Difference (E) Work required to move a unit of charge from one point to another
What is current?
Current is the net flow of charge. It is measured in amperes (C/sec).
What is resistance?
Measure of the ease with which a current flows
Measured in Ohms
E/I
What is conductance? Measurement?
Reciprocal of Resistance (I/E)
Siemens
Relative levels of Na, K, and Cl inside the cell (rather than outside the cell)
High K+ in cell
Low Na and Cl inside
What do ions pass through in a cells?
ion specific channels
What is the ionic equilibrium potential?
An electrical potential difference across the membrane caused by the selective permeability/ionic gradients of the cell membrane.
The thin membrane facilitates what occurance when positive ions leave the cell.
Attraction of negative ions to the opposite side of the membrane.
Is most of the cellular fluid chargeD?
No
T or F. Equilibrium is established when there is no net ion movement across the cell membrane.
True
What influences the rate of flow of an ion across a PM?
Concentration Gradient
Voltage Difference
Conductance of Ion Channels
What is the Nernst equation used for?
Determines the equilibrium potential for a single ion
What is the Nernst equation?
E = [(58mV)/z] x log [(outside ion conc)/(inside ion conc)]
When would you use 61 instead of 58?
Body temp (instead of RT)
What does the principle of electrical neutrality state?
Under biological conditions, the bulk concentrations of cations and anions in a compartment are equal.
What is Donnan Equilibrium a study of?
It shows how the electrical potential across a membrane must balance the conc gradients or K and Cl.
What is the Donnan Equilibrium equation?
[(Kout)(Clout)] = [(Kin)(Clin)]
The Na/K+ pump burns up # ____, pumps out # _______ and takes in # ________.
1 ATP
3 Na
2 K
What is the Goldman Equation?
The nernst equation, but for multiple ions at once.
What does the Goldman equation take into account?
Concentration gradients of different ions and relative permeability of the membrane
What is the Goldman equation?
See page 1-7 (pain to type in)
Ratio of Pk:PCl:PNa
1: 0.45: 0.02
Name three properties that are responsible for maintenance of the transmembrane potential
Transmembrane Resistance (Resting)
Axial Resistance
Membrane Capacitance
What is input resistance? the equation?
relationship btw current injected and change in mem pot.
= (change in V) / I
What determines input resistance?
of ion channels
What is the specific membrane resistance?
The resistance of a unit area of membrane
Input resistance formula using specific mem. resistance
=Rm/(4pir(2))
The greater the area of a cell, the ____ its resistance.
Lower
A neuron smaller neuron fires faster than a larger one because…
(With constant current) the small neuron’s higher resistance will cause a higher E
What is the relationship of membrane resistance and axial resistance to a subthreshold potential value moving down an axon
High Mem. Res = Father Distance Traveled
High Axial Res = Shorted Distance Traveled
What is lambda?
The length constant, distance over which an electric potential decrements to 37% of peak value
What is the equation of lambda?
= sq. rt (Rm/Ri)
Larger Rm = ______ lambda
Larger
Larger lambda increased likelihood of_______
summation
What might the location of the synapse on a cell matter?
Different areas have diff #s of voltage dependent sodium channels
Relationship between diameter and electronic speed?
Synaptic potential will e larger in a small dendritic process than a large one
Larger dendrite will spread farther
What is the membrane time constant?
Time necessary for the electrotonic potential to decree to 37% of its original peak.
Equation for membrane time constant?
(Membrane Resistance) (Membrane Capacitance)
A larger tau means what for summation?
Better chance
